The goal of the Cancer Epidemiology Program (CEP) is to improve our ability to prevent cancer and reduce its burden through new knowledge in surveillance, etiology, patterns of care, and survival, using an interdisciplinary approach. Special emphasis is placed on racial, ethnic, cultural, and other groups with an unequal burden of cancer. This research has been conducted primarily via large populationbased case-control and cohort studies in the ethnically diverse population of the San Francisco Bay Area, which includes Oakland and San Jose. Case-control studies typically collect demographic and exposure data, DNA from peripheral lymphocytes, and/or archived tumor samples. Cohort studies are based on follow-up of healthy individuals for cancer incidence (e.g., California Teachers Study), and of incident cases for cancer care, quality of life, and survival (e.g., CanCORS and Family Registries). Cancer sites of particular interest include breast, ovary, prostate, and lymphomas. This work has been facilitated and enhanced by the recent formal affiliation between Stanford University and the Northern California Cancer Center (NCCC). Some highlights of Program research include findings that oral contraceptive use is associated with reduced ovarian cancer risk and no elevation in breast cancer risk among carriers of BRCA1 mutations, that Helicobacter pylori infection is associated with reduced risk of esophageal cancer, that ethnic differences exist in use of alternative cancer therapies, and that choice of breastconserving surgery is related to socioeconomic status, immigration status and acculturation, and race/ethnicity. The Program adds value to the Cancer Center through its population-based study resources that provide a strong basis for developing important interdisciplinary collaborations and conducting translational research. Dr. Alice S. Whittemore and Dr. Esther M. John lead the Program, both senior cancer epidemiologists with extensive cancer research programs who have worked together for over 15 years. The CEP consists of 23 members, with direct cost funding of $20,220,819, including $6,463,763 in NCI funding. In the period from 2000 to the present, the average number of publications by Program members was 33 per year;of these, 40% were intra-programmatic and 14% were interprogrammatic. Future plans include expanding intra- and inter-programmatic interactions among investigators, identifying new research opportunities, and evaluating the feasibility of a data collection Shared Resource within the Cancer Center.